There should be at least another 1/4 cup of caramelized onions strewn across this tart shell, but they never made it out of the pan. I ate them, a little bit at a time, until I was sure the onions had reached a sufficient level of buttery brown goodness. And that is the problem with this tart. It is elegant and so easy to make—if you can resist eating up all the onions with a spoon!

Caramelized Onion Tart

I was inspired to make up this recipe by a bunch of tennis ball-sized Walla Walla sweet onions that I harvested earlier this fall. They were beginning to sprout, so I cut them in half, removed the green shoots and then sliced them thinly. I ended up with about five cups. You can use any sweet onion in the recipe, and if you have any random white or red onion chunks leftover in the fridge, slice those up and throw them in, too.

What you’ll need:

1 sheet of puff pastry

2 large sweet yellow onions (about five cups thinly sliced)

2 tablespoons butter

Salt

¼ pound Gruyere cheese, grated (about 2 cups)

1 teaspoon fresh thyme leaves

1 egg, lightly beaten

Instructions:

Preheat oven to 400 degrees F. On a floured surface, roll the pastry out into an 8- by 16-inch rectangle. Carefully transfer it to a baking sheet lined with parchment paper. Using a sharp paring knife, score the pastry 2 inches in from the edges to create a rectangular border. Inside the border, use a fork to poke rows of holes spaced at ½ inch intervals. Bake until lightly browned, about 15 minutes. Remove from the oven and set aside. If the center puffed up, use the back of a spoon to depress it, being careful not to crush the border. Don’t worry if the tart shell isn’t a perfect rectangular shape—it tastes just as good when it has lovely rustic borders.

Meanwhile, melt the butter over medium high heat in a large, heavy bottomed dutch oven. Add in the onions, sprinkle them with salt, and toss to coat. After about a minute, when the onions begin to sweat, turn the heat down to medium low. Partially cover the pan and let the onions cook, stirring occasionally, until they are very soft and caramel in color (about 40 minutes). Remove from the heat and set aside.

To assemble the tart, sprinkle half the cheese over the center of the pastry shell. Sprinkle the onions and thyme in an even layer over the cheese. Top the onions with the remaining cheese. Brush the border with the egg wash. Return the tart to the oven and bake until it is heated through and the edges are a deep golden brown (10 to 15 minutes).

Be Sociable, Share!

•